Variable output welding transformer



Dec. 6, 1949 E. A. HOBART 2,490,354

VARIABLE OUTPUT WELDING TRANSFORMER Filed Oct. 22, 1947 4 She etSSheet l INVENTOR EDWARD A 031m? ATTORNEYS a 6, 1949 E. A. HOBART VARIABLE OUTPUT WELDING TRANSFORMER 4 Sheets-Sheet 2 Filed Oct. 22, 1947 INVENTOR EDWARD A. HOBAR? ATTORNEYS JWMW Dec. 6, 1949 Filed Oct. 22, 1947 E. A. HOBART VARIABLE OUTPUT WELDING TRANSFORMER 4 Sheets-Sheet 3 INVENTOR EDWARD A HOBART ATTORNEYS Dec. 6, 1949 E. A. HOBART 4 2,490,354

VARIABLE OUTPUT WELDING TRANSFORMER Filed Oct. 22, 1947 4 Shets-Sheet 4 INVENTOR EDWARD A. HOBART Twww'm & ATTORNEY5 Patented Dec. 6, 1949 VARIABLE OUTPUT WELDING TRANSFORMER Edward A. Hobart, Troy, Ohio, assignor to The Hobart Brothers Company, Troy,

poration of Ohio Ohio, a cor- Application October 22.1947, Serial No. 781,341

8 Claims. 1

This invention relates to transformers of the type commonly employed in conjunction with welding and is concerned primarily with such a transformer having a variable output.

At the present time it is a common and well accepted practice in the field of arc welding to employ a transformer for the alternatingcurrent which may be adjusted to vary the amperage output. Thus, the transformer may be adjusted to accommodate the particular requirements of any specified job.

With the now known variable output transformers one of the coils which may be either the primary or secondary is anchored in a fixed posi-* tion whereby it is rendered stationary. The other of the coils is then mounted so that it is movable with respect to the fixed coil. The amperage of the current which is delivered by the transformer depends directly on the relative position of the primary and secondary coils. Thus, by adjusting this relative position the amperage is varied as occasion demands.

With the above noted conditions in mind the present invention has in view, as its foremost objective, the provision of a variable output transformer of the type indicated in which both the coils are movably mounted. In carrying out this idea the coils are vertically arranged and mounted on a screw stern having oppositely threaded sec tions. of the threaded sections and the other coil from the other threaded section. This arrangement presents certain definite advantages.

Due to the vertical disposition of the coils any relative movement therebetweenis accompanied by the movement of one coil against the force of gravity, while the movement of the other coil is aided by gravity action. By mounting the coils in the manner above specified the two movements are compensatory and all adjustments are made with minimum ease and require a uniformity of exertion. Thus, we do not have the condition which previously existed wherein one coil could be easily lowered with very little effort but which ,was raised only with a much greater exertion. With the arrangement of this invention the same effort is required to move the coils together as it is to separate the By mounting both of the coils on the oppositely threaded stem the time required for making any i particular adjustment is greatly reduced. It is to be remembered that there is a definite limit as to the pitch of the screw threads which'may be employed. If this pitch is too great, one of the coils could slide down the screw threads under One of the coils is supported from one :1

the influence of gravity action. Hence, the pitch of the threads must be held within a certain limit. For any given pitch one turn of the screw stem will move the coils together at twice the rate which would obtain were only one of the coils movably mounted on the stem.

With the variable output transformers heretofore employed great difilculty has been experienced ,in eliminating or holding to a desirable minimum the hum or noise which attends the magnetic vibration. This is largely due to the fact that when a movable core type of transformer is employed any metal part through which the magnetic flux passes is subject to vibration and becomes noisy unless the fits are highly accurate.

If the core is fixed and one coil is stationary, the latter is securely afllxed to the magnetic core. The screw which operates the movable coil of necessity has to be supported at the two ends by bearings and these bearings are subject to the same vibration and noise that attend the movable core.

Another highly important object of the present invention is the reduction or substantial elimination of this magnetic vibration. This is achieved by the above outlined arrangement by which both of the cores are movably mounted on the screw stem having oppositely threaded sections. With this arrangement none of the vibration is transmitted to the bearings as it occurs only between the two supports suspended from the screw and these supports substantially counterbalance each other. Due to the fact that a small pitch may be employed there are many threads which are effectively engaged by each nut that supports the coils. These threads substantially eliminate any vibration between the coil supporting nut and the stem.

Various other and more detailed objects and advantages of the invention such as arise in connection with carrying out the above noted ideas in a practical embodiment will in part become apparent and in part be hereinafter stated as the description of the invention proceeds.

The invention, therefore, comprises a variable output transformer designed primarily for welding purposes and which is characterized by movably mounting both the primary and secondary coils on oppositely threaded sections of a screw stem. This stem may be rotated to adjust the relative position of the coils and thereby vary the amperage output of the transformer.

For a full and more complete understanding of the invention, reference may be had to the follow- 3 ing description and accompanying drawings wherein: v

Figure 1 is a perspective view of a welding transformer designed in accordance with the precepts of this invention;

Figure 2 is a horizontal section through the transformer being taken about on the plane represented by the line 2-2 of Figure 3;

Figure 3 is a vertical section taken on an enlarged scale;

Figure 4 is another vertical section. taken normal to the showing of Figure 3;

Figure 5 is an enlarged detailed view mostly the mounting at the lower end of the screw stem; and

' in elevation'but partially in section bringing out Fig. 6 is a detailed view of the core frames per se.

Referring now to the drawings wherein like reference characters denote corresponding parts and first more particularly to Figures 3 and 4, the welding transformer of this invention is shown as comprising a base Hi from which depend feet H which are adapted to rest on any desirable supporting surface. A casing is identified in its entirety by the reference character C. This casing comprises a lower base section 62 of cylindrical formation and which includes a bottom it formed with an opening that receives the base 85. Upstanding from the base section 52 is a main intermediate body section H1 which may be anchored to the base section l2 in any preferred manner such as by the rivets shown at B5.

The intermediate body section id is formed with a rear opening it which normally is closed by a door Ill. The latter may be opened to provide access to the interior of the casing from the rear. Substantially diametrically opposite to the rear opening it the body section it is formed with a front opening it that is normally closed by a frontdoor it. By opening the door l9 access to the interior of the casing from the front ,may be had through the opening 58.

Immediately above the main intermediate body section it the casing C includes a ventilating section 29. The cap for the casing C is designated 2i and is shown as having a skirt Z2,that overlaps the ventilating section to which it is joined. The cap 2i is formed with a window opening at 23 that is normally covered by a transparent pane 24. The cap 2i includes a top wall 25 formed with a central opening 25 that is closed by a handwheel 21 that carries an operating member in the form of a knob 28. Upstanding from the base ill are two frame end pieces 29 and 353 between which extend intermediate side braces 3i and 32. Extending between the end pieces 25 and 36 at a distance slightly spaced from the upper ends thereof is a shroud 33 that takes the form of a plate which is anchored to the end pieces by angle bars 341. This plate 33 is formed with a circular opening 35 (see Figures 2 and 3) which accommodates fan blades 36. The fan blades 35 are mounted on the shaft 31 of a motor 38 that is supported from the cross braces 3i and 32 by the ears 39 which are anchored thereto.

Resting on the top of theend pieces 29 and 3E? is a core assembly which is identified in its entirety by. the reference character A. This core assembly A comprises two complemental open frames F1 and F2. These frames are maintained in assembled relation by a bottom piece it of channel construction which is supported by the end pieces 29 and 3d and anchored thereto by the bolt and nut assembly shown at M. A top piece 42 which is also of channel construction aids in maintaining the asembled relation of the frames F1 and F2. 1

Between the framestF1 and F2 there is defined a central passage or recess 53 for a purpose to be later explained. Inasmuch as the frames F1 and F2 are of complemental or duplicate construction, only one of them needs here be described in detail for the purposes of this specificatlon.

Upon referring to Figure 4, it will be noted that each of these core frames comprises a front frame member 55 and a rear frame member 35, the two being of angle bar construction. The top piece which has been identified generally as 32 also comprises a pair of angle bars which 'are anchored to the frame members 15 and 55 by the bolts shown at 56. The frame members 65 and 55 include upper and lower side portions ll and 58, respectively, which are ofi-set with relation to each other and joined by a shoulder 39. Each of the frames F1 and F2 includes a centrally disposed core piece 5@.

It is notable that the side parts 58 are anchored to the bottom piece which has been identified generally as 35 by bolts shown at 5!. This bottom piece 65 actually takes the form of the two angle bars that are clearly brought out in Figure 4 and which are anchored to the end pieces 25 and 3G by the bolts 5!. Laminations shown at 9 are clamped between the front and rear angle bars making up the frames F1 and F2. It is evident that the frame F1 provides an upper space 52 and a lower space 53 with the latter larger than the space 52 which increased dimension is provided by the shoulders 39.

One coil of the transformer which, for illustrative purposes, may be taken as the primary coil is shown at 58. This coil is disposed about the central core frame parts 58 and is designed for vertical reciprocation mainly within the spaces 52 although the coil 55 may be moved down into the larger spaces 55. The other coil which, in this instance, will be the secondary is shown at 55 which is also disposed about the central core frame parts 55. The coil 55 is designed for vertical reciprocation in the larger spaces 53 and has a central bore represented by the broken lines of Figures 3 and 4; which is sumciently large to receive the coil 55. Thus, the coil 55 is adapted to be received either partially or entirely within the coil 55.

A screw stem 55 extends from the handwheel 21 at the top down between the angle bars making up the'top piece d2, through the passage or space 53, between the frames F1 and F2 into the bottom piece 5B where the lower end is received between the angle bars making up this piece. This screw stem 5S has oppositely threaded screw sections 5? and 58. As shown in Figure 3, the lower end of the screw stem 56 is received in a bearing assembly 59 carried by thehottom piece cc and its upper end passes through another bearing assembly 60 carried by the top piece &2.

The coil 55 is anchored to a support Si by the nut and bolt assembly shown at 62. The support 6| has an opening through which the screw stem passes and carries a nut 63 into which is threaded the screw section 58. Thus, the coil section 55 is supported from the screw section 53.

Likewise, the coil 55 is anchored to a support so by bolts comparable to the bolts 52 and the support t l carries a nut to that is threaded into the screw section 51 of the stem 50. Thus, the coil 54 is supported from the screw section 51. The upper end of the screw stem 56 is drivably connected to the handwheel 21 by the connection shown at 66.

Positioned within thecap 2| at a point where it may be viewed through the window opening 23 is a dial face 61 which takes the form of a segment of a cylinder. The dial face 6! is carried by a plate 68 which in turn carries a sheave 69 that is freely journaled about the screw stem 56. A coil spring 10 is disposed about the screw stem 55 and has a tendency to normally urge the dial face 81 in one direction of rotation. A cable H is positioned over the sheave 69 and tension on this cable opposes the tendency of the spring Ill. Thus, if this tension is suiliciently great, the dial face 61 is rotated in a direction opposite to that caused by the spring 10.

A lever 12 is pivotally mounted as indicated at 13 on the rear frame part 45 of the frame F2 back of the shoulder 49 of this frame. The upper end'of the lever 12 carries a hook 14 to which the cable H is anchored. A bar 15 is secured to the coil support 64 and carries at its free end a roller 16 that engages the arm T2. The pivot 13 for the lower end of this lever 12 is so positioned that when the coil 54 moves upwardly the roller 16 urges the lever 12 outwardly thereby exerting a tension on the cable H and rotating the dial face 61 against the influence of the spring 10. When the coil 54 is lowered the roller 16 is retracted and the spring 10 becomes effective to rotate the dial face 67 in the opposite direction. This mechanism for actuating the dial face is illustrated, described, and claimed in the copending application of Edward A. Hobart et al., Serial No. 727,830, filed February 11, 1947, entitled Alternating current vertical welder. Said application issued as Patent 2,457,3'72 on December 28, 1948.

Opposite to the opening it there is a panel I? which carries a terminal represented at 18. Access to this panel may be had by opening the door i1. Likewise, there is another panel 19 opposite to the opening l8 and this panel carries a terminal shown at 80. These terminals I8 and 80 are used in making the electric connections to the primary and secondary coils 54 and 55.

As is clearly brought out in Figure 4, a pair of condensers may be carried by the base l beneath the shroud 33.

Operation While the operation of the above described mechanism is believed to be obvious, it may be briefly described by noting that when the user of this welding transformer is desirous of adjusting the amperage output he avails of the knob 28 to rotate the handwheel 21. A corresponding rotation is thereby imparted to the screw stem 56 and depending on the direction of rotation the primary coils 54 and 55 are either moved in a direction tending to separate them or towards each other.

As the amperage output depends on the relative position of these coils 54 and 55, any adjustment in this relative position is accompanied by a turning of the dial face 51 whereby the operator may be reading this dial face to ascertain just what current is being delivered by the trans former.

While the preferred specific embodiment of the invention is hereinbefore set forth, it is to be clearly understood that the invention is not to be limited to the exact construction illustrated and described, because various modifications of these details may be provided in putting the invention into practice within the purview of the appended claims.

What is claimed is:

1. In a welding transformer, a substantially vertical screw stem having oppositely threaded sections, a primary coil supported from one of said threaded sections and having its axis coincident with said stem, and a secondary coil supported from the other of said threaded sections and having its axis coincident with said stem, said coils being independent of one another so far as direct electrical connections are concerned.

2. In a welding transformer, a screw stem having oppositely threaded sections, a primary coil disposed about said screw stem and supported from one of said threaded sections, and a secondary coil also disposed about said screw stem and supported from the other of said threaded sections, one of said coils being larger than the other and having a bore sufficiently great to receive the smaller of said coils.

3. In a welding transformer, a screw stern having oppositely threaded sections, a primary coil disposed about said screw stem and supported from one of said threaded sections, and a secondary coil also disposed about said screw stem and supported from the other of said threaded sections, said secondary coil being larger than said primary coil and having a bore sufllciently large to receive said primary coil.

4. In a welding transformer, a screw stem having oppositely threaded sections, a primary coil disposed about said screw stem and supported from one of said threaded sections, a secondary coil also disposed about said screw stern and supported from the other of said threaded sections, and a hand-wheel carried by said screw stem and operable to rotate said screw stem.

5. In a welding transformer, a screw stem having oppositely threaded sections, a pair of core frames arranged on opposite sides of said screw stem, each of said core frames defining upper and lower spaces, one larger than the other, a primary coil disposed in one pair of corresponding of said spaces and about said screw stem, means for supporting said primary coil from one of said threaded sections, a secondary coil in the other pair of said spaces. means for supporting said secondary coil from the other of said threaded sections, and means slidably guiding said coils on said core frames and preventing rotation of said coils whereby rotation of said screw stem will move said coils relatively.

6. In a welding transformer, a casing, a screw stem mounted in said casing and having oppositely threaded sections, a pair of core frames arranged on opposite sides of said screw stem so as to define a passage enclosing said screw stem and rigidly connected together, each of said core frames defining an upper reduced space and a lower enlarged space, a primary coil positioned in the upper spaces of said core frames about said screw stern, means for supporting said primary coil from one of said threaded sections. a secondary coil positioned in the larger spaces of said core frame about said screw stem, means for supporting said secondary coil from the other of said threaded sections, and means slidably guiding said coils on said core frames and preventing rotation of said coils whereby rotation of said screw stem will move said coils relatively.

aeaassa 7. In a welding transformer, a screw stem having oppositely threaded sections, a pair of core frames on opposite sides of said screw stem defining a passage enclosing said screw stem and having walls parallel with the axis of said screw stem, means rigidly connecting said frames together and journalling said screw stem at its opposite ends, a nut screwed onto each threaded section of said stem, a coil support carried by each nut and in sliding engagement with the walls of said passage, a primary coil anchored to one of said supports, and a secondary coil anchored to the other of said supports, whereby rotation of said screw stem will move said coils relatively, and said coils being adapted for telescoping together.

8. In a welding transformer, a primary coil, a secondary coil, said coils being adapted for telescoping, a. pair of independent magnetic core frames extending through and around said coils, said frames being spaced apart and rigidly connected together at their ends, whereby they define a passage having parallel walls, supporting means connected with said coils and engaging said walls for slidably guiding said coils in relatively rectilinear reciprocation whereby the a smaller of said coils may be telesooped to any desired degree with the larger of said coils, and means extending along said passage and connected with said supporting means operable for moving said coils in respectively opposite direc tions for varying the coupling therebetween, said means also being operable for rigidly retaining said coils in any of their positions of adjustment relative to each other.

mwann A. HOBART.

RMERENGES mm The following references are of record in the file of this patent:

D STATES PAS Rosenberg June 2, 1942 

